Polyethylene is $9 for 100 foot roll making it cheaper, but it's not only the cost savings. It's also better because it has a smaller inside diameter and lets the air flow better. It also releases easier from the fittings (when you want it to). Polyurethane certainly has some advantages (such being more durable and flexible then polyethylene). But my point was that for our industry polyethylene is the airline of choice.

As to worrying about the "hardness rating" my point was that is just adding an unnecessary level of complexity to the conversation which only serves to confuse people. One of my missions is to educate people as to how easy it is to get into this stuff. I was trying to point out that having to know that piece of information is unnecessary.

I'll throw my cents in on polyethylene vs polyurethane, as IMO both are right for our industry.

Polyurethane is a premium product, with a premium price tag. It offers superior abrasion resistance and is FAR more flexible than polyethylene or nylon. Polyurethane will handle the lowest pressure of the three, but all three offer much higher working pressures than most haunts will ever deal with. Both poly's are neck and neck when it comes to heat. In high heat applications (IE, my compressor controller where I didn't want to have to run copper), I use Nylon. With respect to inside diameter, my Freelin Wade polyurethane is spec'ed at .16 ID, my ATP polyurethane is .156. Freelin Wade polyurethane is .17 and Nylon is .18. So yes, polyethylene will flow, what, maybe a percent better than polyurethane? I don't believe that will have any real impact on a haunted house prop.

I much, much prefer working with polyurethane. That's not to say polyethylene is a bad product, it's not, I just prefer urethane. The only thing that I dislike about urethane is pulling multiple lines through a bridal ring or the like. The tubing likes to stick to other tubing and attempt to pull it's neighbors with it. But that is a installation issue more than anything and something I got used to dealing with this summer. With the elevator project this year, I went through 650' of 1/2" urethane, 1300' of 1/4" urethane and ~100' of 3/8" urethane. Most all of which was pulled through bridal rings.